Acute alterations of tissue Ca++ and lethal tubular cell injury during HgCl2 nephrotoxicity in the rat

Calcium in cell injury and death

Loss of Ca(2+) homeostasis, often in the form of cytoplasmic increases, leads to cell injury. Depending upon cell type and the intensity of Ca(2+) toxicity, the ensuing pathology can be reversible or irreversible. Although multiple destructive processes are activated by Ca(2+), lethal outcomes are determined largely by Ca(2+)-induced mitochondrial permeability transition. This form of damage is primarily dependent upon mitochondrial Ca(2+) accumulation, which is regulated by the mitochondrial membrane potential. Retention of the mitochondrial membrane potential during Ca(2+) increases favors mitochondrial Ca(2+) uptake and overload, resulting in mitochondrial permeability transition and cell death. In contrast, dissipation of mitochondrial membrane potential reduces mitochondrial Ca(2+) uptake, retards mitochondrial permeability transition, and delays death, even in cells with large Ca(2+) increases. The rates of mitochondrial membrane potential dissipation and mitochondrial Ca(2+) uptake may determine cellular sensitivity to Ca(2+) toxicity under pathological conditions, including ischemic injury.

Cytoprotective effects of calbindin-D(28k) against antimycin-A induced hypoxic injury in proximal tubular cells

Intracellular calcium plays an important role on the pathogenesis of hypoxia-induced cellular injury. Calbindin-D(28k), a cytosolic vitamin D-dependent calcium binding protein, can serve as a buffer to limit a surge in intracellular Ca2+ concentration ([Ca2+]i) induced by various stimulations. To evaluate the possible cytoprotective effect of calbindin-D(28k) against hypoxic injury in proximal tubular cells, a plasmid containing calbindin-D(28k) cDNA under the control of CMV immediate-early gene promoter was transfected into the murine proximal tubular epithelial (MCT) cells. The expression of calbindin-D(28k) in the transfected cells was verified with Northern blot analysis, Western blot analysis, and immunofluorescent staining. The non-transfected and transfected MCT cells were subjected to chemical hypoxia induced by antimycin A (10 microM) and glucose deprivation for 30-120 min. The transfection of calbindin-D(28k) reduced lactate dehydrogenase (LDH) release by 41%, 41%, 24%, and 24%, respectively, at 30, 60, 90 and 120 min after hypoxia when compared to the non-transfected cells (all p < 0.05). Cell viability after hypoxic injury was also significantly higher in transfected cells than non-transfected cells. Transfection with the plasmid without calbindin-D(28k) cDNA did not affect LDH release or cell viability after chemical hypoxic injury. [Ca+2]i was measured ratiometrically with fura-2 after exposure to chemical hypoxia. The rate of initial rise in [Ca2+]i and final [Ca+2]i at 30-120 min were significantly lowered in transfected cells. In conclusion, this study demonstrated that transfection of calbindin-D(28k) gene into MCT cells provide protective effects against chemical hypoxic injury probably through its buffering effects on [Ca+2]i.

Nephrotoxicity of xenobiotics

Nephrotoxicity can be grouped by the xenobiotics place of action, by the clinical presentation or by the generic toxic effect. The latter can be dose related, indirect, idiosyncratic or allergic. Nephrotoxicity of lithium, demeclocycline, aminoglycosides, cyclosporine, mercuric ion, nonsteroidal anti-inflammatory drugs, methoxyflurane, ethylene glycol, D-penicillamine and methicillin is reviewed in light of all these three viewpoints, but emphasis is on toxic mechanisms.

Evidence that mercury from silver dental fillings may be an etiological factor in multiple sclerosis

This paper investigates the hypothesis that mercury from silver dental fillings (amalgam) may be related to multiple sclerosis (MS). It compares blood findings between MS subjects who had their amalgams removed to MS subjects with amalgams. MS subjects with amalgams were found to have significantly lower levels of red blood cells, hemoglobin and hematocrit compared to MS subjects with amalgam removal. Thyroxine levels were also significantly lower in the MS amalgam group and they had significantly lower levels of total T Lymphocytes and T-8 (CD8) suppressor cells. The MS amalgam group had significantly higher blood urea nitrogen and lower serum IgG. Hair mercury was significantly higher in the MS subjects compared to the non-MS control group. A health questionnaire found that MS subjects with amalgams had significantly more (33.7%) exacerbations during the past 12 months compared to the MS volunteers with amalgam removal. The paper also examines epidemiological correlations between dental caries and MS; as well as how mercury could be causing the pathological and physiological changes found in multiple sclerosis.